Catching Apparatus

ABSTRACT

A downhole catching apparatus ( 20 ) comprises a plurality of radially moveable seat members ( 26 ) arranged circumferentially around a longitudinal axis, wherein the seat members are moveable between a radially extended configuration which permits passage of an object ( 64 ) therethrough and a radially retracted configuration which permits an object ( 64 ) to be caught by the apparatus. A releasable lock arrangement ( 44 ) is provided for releasably retaining the seat members in the radially extended configuration.

FIELD OF INVENTION

The present invention relates to a catching apparatus for use incatching an object, such as within a downhole flow path.

BACKGROUND TO INVENTION

In the oil and gas industry many downhole operations rely on objectsdropped from surface to be caught at some point along a downhole systemto perform a desired function, such as mechanical actuation, flowdiversion or the like. For example, WO 2011/117601 and WO 2011/117602each disclose downhole apparatus which catch objects for use inactuation of a downhole tool and flow diversion within the tool, forexample for use in fracturing operations.

A collet type catching apparatus includes a number of collet fingerseach carrying a collet or seat member. In use, the collet fingers arecapable of being deflected radially inwards to move the seat membersbetween the radially extended configuration and a radially retractedconfiguration which permits an object to be caught.

In some circumstances, however, it is possible for the collet fingers toinadvertently move to the radially retracted configuration, impairingthe passage of an object or tool through the downhole system.

Inadvertent movement of the collet fingers to the radially retractedconfiguration may occur, for example, where residual stresses retainedin the apparatus from its manufacture are released when the apparatus issubject to repeated impact events during its operational life, such asfrom the impact of an object or objects to be caught by the apparatus.

SUMMARY OF INVENTION

According to a first aspect of the present invention there is provided adownhole apparatus, such as a catching apparatus for catching an object,comprising:

a plurality of radially moveable seat members arranged circumferentiallyaround a longitudinal axis, wherein the seat members are moveablebetween a radially extended configuration and a radially retractedconfiguration; and

a releasable lock arrangement configured to retain the seat members inthe radially extended configuration.

The radially extended configuration may permit passage of an objectthrough the seat members and the radially retracted configuration maypermit an object to be caught by the apparatus/seat members.

Providing a lock arrangement may permit the seat members to be retainedin the radially extended configuration and so prevent inadvertentmovement or collapse of the seat members towards a radially retractedconfiguration, for example as a result of impact of an object on theseat members. Providing a lock arrangement may permit the seat membersto be retained in the radially extended configuration without relianceon equalised stresses in the apparatus to keep them in position.

The apparatus may be configured to be retained in the radially extendedconfiguration until acted on by an actuation event. Retaining theapparatus in the radially extended configuration until acted on by anactuation event may ensure that the apparatus is not collapsed until anoperator wishes to actuate the tool.

The lock arrangement may define a locked condition and an unlockedcondition.

The lock arrangement may be biased towards the locked condition. Thelock arrangement may be biased towards the locked condition by a biasingmember, such as a spring or the like.

The lock arrangement may be configured to move from the locked conditionto the unlocked condition. The lock arrangement may be configured tomove from the locked condition to the unlocked condition to permitmovement of the seat members towards the retracted configuration. Thus,the apparatus may be retained until it is desired to release the lockarrangement.

The lock arrangement may be configured to move from the locked conditionto the unlocked condition by axial movement. The actuation event maycomprise the axial movement.

The lock arrangement may be configured to move from the unlockedcondition to the locked condition. The lock arrangement may beconfigured to move from the unlocked condition to the locked conditionto permit the seat members to again be retained in the extendedconfiguration. Thus, the lock arrangement may be re-useable, beingmoveable between the locked condition and the unlocked condition aplurality of times. The lock arrangement may be configured to move fromthe locked condition to the unlocked condition by axial movement.

At least part of the lock arrangement may be defined by a seat member.

At least part of the lock arrangement may be defined by a housing. Theapparatus may comprise the housing or the housing may be operablyassociated with the catching apparatus.

At least part of the lock arrangement may be defined by a tool. Theapparatus may comprise the tool or the tool may be operably associatedwith the catching apparatus. The tool may be disposed about the seatmembers. The tool may be disposed between the housing and the seatmembers.

The tool may comprise an annular member. The tool may comprise a ring, awasher or the like.

The tool may comprise a sleeve, such as an insert sleeve, disposedwithin the housing. The insert sleeve may be secured to the housing.Providing an insert sleeve may assist in manufacture of the lockarrangement.

In particular embodiments, the lock arrangement may be defined by theseat members, the annular member, such as the ring, and thehousing/insert sleeve.

The lock arrangement may comprise a lock profile.

The lock profile may comprise an external profile. For example, the lockprofile may comprise an external profile formed or otherwise provided onone or more of the seat members.

The lock profile may comprise an internal profile. For example, the lockprofile may comprise an internal profile formed or otherwise provided onthe annular member, such as the ring. Alternatively, or additionally,the lock profile may comprise an internal profile formed or otherwiseprovided on the housing or insert sleeve.

In particular embodiments, the lock profile may be defined by anexternal profile on the seat members, and internal profiles on the ringand insert sleeve. The internal profiles may be axially spaced.

In use, the lock profiles may cooperate to retain the lock arrangementin the locked condition.

The apparatus may be configured to define multiple lockedconfigurations. For example, in a first locked configuration the seatmember lock profile may be arranged to cooperate with the annular memberlock profile. In a second locked configuration the seat member lockprofile may be arranged to cooperate with the housing or insert sleevelock profile.

The, or at least one, lock profile may comprise a hook profile, a barb,or the like.

The, or at least one, lock profile may comprise an acute angle. Inparticular embodiments, the, or at least one, lock profile may comprisean angle of 50 degrees. The angle may alternatively be, for example, 30degrees, 45 degrees, 60 degrees, 70 degrees, or any other suitableangle.

The lock arrangement, more particularly the lock profile or profiles,may assist in providing erosion protection. This may be achieved sincethe profile, or profiles, define more material to be eroded shoulderosion occur. Thus the profile, or profiles, may be at least partiallysacrificial.

At least one of the apparatus, the seat members, housing, annularmember, sleeve, ring may be provided with or comprise an erosionresistant coating. Providing an erosion resistant coating may assist inproviding erosion protection.

The catching apparatus may be configured to catch an object such as aball, dart, plug, tool or the like.

The catching apparatus may be for use in catching an object passingalong any flow path, such as in a pipeline environment, downholeenvironment or the like.

The catching apparatus may be configured to catch an object travellingin a downhole environment, for example travelling through a tubularstructure positioned within a wellbore, such as a tubing string,completion string, tool string, production string, injection string,fracturing string or the like. The catching apparatus may be configuredto be located within a tubular structure. For example, the catchingapparatus may be configured to be mounted within a housing of a downholetool.

The catching apparatus may define a catching sleeve. In such anarrangement the apparatus may be provided in the form of a sleeve.

The catching apparatus may be configured to function as a flow diverterwhen an object is caught.

The catching apparatus may be configured to function as an actuator whenan object is caught. For example, the catching apparatus may beconfigured to actuate another component, structure, apparatus, tool orthe like. For example, when an object is caught by the catchingapparatus, the object may facilitate movement of the catching apparatus,for example by impact of the object against the apparatus, by a pressuredifferential established across the object/catching apparatus, or thelike.

The catching apparatus may be provided in combination with a j-slotactuator arrangement.

The catching apparatus may be configured to function as a bore plug whenan object is caught, for example to isolate a region within a tubingstructure. Such an arrangement may facilitate pressure to be controlled,for example elevated, in a section of a tubing structure. Such anarrangement may facilitate pressure actuation of a further component,structure, apparatus, tool or the like, such as packers, slips, rupturedisks and the like.

The catching apparatus may be configured to function as a flowrestrictor when an object is caught. For example, the catching apparatusmay be configured to function as a choke.

The catching apparatus may be configured for use within a fracturingsystem or operation. For example, the catching apparatus may beconfigured to actuate or open one or more fracturing valves to permit afracturing fluid to be delivered into a surrounding formation.Alternatively, or additionally, the catching apparatus may be configuredto function as a flow diverter when an object is caught to divert flowof fracturing fluid outwardly through opened ports and into asurrounding formation.

The seat members may be radially moveable to be radially extended andretracted relative to a central bore of the catching apparatus. That is,the seat members may be moveable radially inwardly to be retracted intothe central bore to define a reduced effective inner diameter. The seatmembers may be moveable radially outwardly to be radially extended fromthe central bore to define an increased effective inner diameter. Whenthe seat members are positioned radially inwardly and retracted into thecentral bore said members may be positioned into the path of an objectpassing through the catching apparatus. When in such a configuration theseat members may be engaged by an object. When the seat members arepositioned radially outwardly and extended from the central bore saidmembers may be outside the path of an object passing through thecatching apparatus.

The catching apparatus may be configurable from a free configuration inwhich the seat members permit an object to pass the catching apparatus,to a catching configuration in which the seat members catch an object.

The catching apparatus may be reconfigured to or in its catchingconfiguration by radially supporting the seat members in a radiallyinward position such that outward radial movement is prevented. In sucha configuration an object passing through the catching apparatus maybecome seated against the radially supported seat members.

The catching apparatus may be configurable between its free and catchingconfigurations by an actuator. Any suitable actuator may be used toactuate and reconfigure the catching apparatus. For example, a valvemember, such as a valve sleeve, arranged in proximity to the catchingapparatus may function to reconfigure the catching apparatus. Forexample, opening and/or closing of a valve member may also reconfigurethe catching apparatus.

An indexing sleeve, such as a collet sleeve disclosed in WO 2011/117601and/or WO 2011/117602 may be used to reconfigure the catching apparatus.The disclosure of WO 2011/117601 and WO 2011/117602 is incorporatedherein by reference.

A piston assembly may be used to reconfigure the catching apparatus. Ashifting tool, such as a coiled tubing or wireline deployed shiftingtool may be used to reconfigure the catching apparatus.

The seat members may be biased in a radial direction.

In one embodiment the seat members may be biased radially outwardly. Insuch an arrangement the seat members may require to be positively movedagainst this bias to be moved radially inwardly and be retracted intothe central bore to be engaged by an object. Thus, when the catchingapparatus is in its free configuration an object may freely pass throughthe catching apparatus without or with minimal engagement with the seatmembers. The catching apparatus may be reconfigured into its catchingconfiguration by positively moving the seat members radially inwardlyinto the central bore against the bias to catch an object.

In one embodiment the seat members may be biased radially inwardly. Insuch an arrangement the seat members may be required to be positivelymoved against this bias to be moved radially outwardly and be extendedfrom the central bore to allow passage of an object, when required. Suchoutward radial movement of the seat members may be caused by an objectacting against the seat members during passage of the object through thecatching apparatus when the catching apparatus is configured in its freeconfiguration.

The catching apparatus may be axially moveable to be configured betweenits free and catching configurations.

The catching apparatus may be held stationary and a support arrangement,such as a sleeve, may be moved axially relative to said catchingapparatus to selectively support the seat members in a radially inwardposition.

The catching apparatus may be configurable from the catchingconfiguration to a release configuration in which the seat memberspermit release of a previously caught object.

In one embodiment the catching apparatus may be configurable to therelease configuration by de-supporting the seat members. When the seatmembers are de-supported a bias force may act to move the seat membersradially outwardly and extend the seat members from the central bore.Alternatively, or additionally, when the seat members are de-supporteddisplacement of an object, for example by fluid pressure, may deflectthe seat members radially outwardly, thus allowing the object to pass.

The catching apparatus may be axially moveable to permit said catchingapparatus to be reconfigured to the release configuration. Such axialmovement may be achieved by action of an object seated against the seatmembers, for example by action of a differential pressure permitted tobe established across the interface between the object and the seatmembers.

The catching apparatus may be axially moveable to align the seat memberswith a region of increased inner diameter, thus permitting the seatmembers to be moved radially outwardly.

The catching apparatus may be provided in combination with a releasearrangement. The catching apparatus and the release apparatus may formpart of a catching system according to an alternative aspect of thepresent invention. The release arrangement may be actuated by axialmovement of the catching apparatus. The release arrangement may beconfigured to facilitate de-supporting of the seat members to permit thecatching apparatus to be configured in its release configuration.

The release arrangement may comprise a release sleeve. The releasesleeve may be moveable between a supporting position in which therelease sleeve may radially support the seat members in the radiallyinward or retracted position, towards a de-supporting position in whichthe release sleeve removes the radial support to the seat members,allowing the seat members to be moved radially outwardly.

The release sleeve may cover a release recess, for example formed withina tubing structure, when said release sleeve is located within itssupporting position. The release sleeve may be moved axially towards itsrelease position to uncover the release recess and permit the seatmembers to be moved radially outwardly and received within the releaserecess to permit release of an object.

The release sleeve may be moved axially by an actuator.

The release sleeve may be moved axially by the catching apparatus,

The release sleeve may define a load profile, such as a load shoulder,configured to be engaged by the catching apparatus.

The catching apparatus may define a load profile configured to engage aload profile on the release sleeve to permit the catching apparatus toapply a force on the release sleeve.

One or more seat members may comprise a load profile, such as a notch,configured to engage a load profile on the release sleeve to permit therelease sleeve to be moved by the catching apparatus. One or more seatmembers may comprise a load profile on a radially outer surface thereofand configured to engage a corresponding load profile, such as anannular shoulder, on a radially inner surface thereof.

Each seat member may comprise a load profile, wherein when said seatmembers are moved radially inwardly the individual load profiles definea substantially circumferentially continuous load profile.

The catching apparatus may be biased in a preferred axial direction.Such bias may be provided by a spring, for example. In some embodimentssuch bias may be provided in a direction to permit the catchingapparatus to be configured in its free configuration. In one embodimentthe catching apparatus may be biased in a direction opposite to thedirection in which a release sleeve is moved to be positioned within arelease position. Such an arrangement may permit the catching apparatusto be axially returned, following actuation of the release sleeve, to aposition at which the seat members may be aligned with an uncoveredrelease recess.

The seat members may collectively define a substantially completeannular structure when positioned radially inwardly, for example whenthe catching apparatus is configured within its catching configuration.In such an arrangement each seat member may be engaged or be broughtinto very close proximity with circumferentially adjacent seat memberswhen positioned radially inwardly.

The ability to provide a substantially complete annular structure maypermit a high degree of sealing to be achieved between the seat membersand an object when seated against the seat members. The ability toprovide a substantially complete annular structure may permit a morerobust structure to be formed, which may facilitate improved mechanicalresponse to the operational forces, such as impact forces uponengagement by an object, actuation forces by an object seated againstthe seat members, resistance to extrusion forces and the like.

One or more seat members may define a seat surface on one axial sidethereof. Such a seat surface may be configured to be engaged by anobject.

The seat surface of a seat member may be arranged to provide asubstantially continuous or complete engagement with an object. Such anarrangement may permit sealing engagement to be achieved between theseat surface and an object. In one embodiment the seat surface maydefine a circumferential profile which corresponds to a circumferentialprofile of an object.

One or more seat members may define a curved seat surface. One or moreseat members may define a convex seat surface. Such an arrangement maybe provided in combination with use of an object having a curved, suchas convex, surface.

One or more seat members may be configured to be engaged by an objectfrom opposing axial directions. Such an arrangement may permit an objectto be caught or arrested when passing in either axial direction. Forexample, in some embodiments reverse flow through the catching apparatusmay cause an object which has previously passed in a forward directionto be engaged or seated against the seat members. Further, such anarrangement may permit the catching apparatus to be actuated to move inopposing axial directions in response to engagement by an object ineither axial direction.

One or more seat members may comprise a first seat surface on one axialside thereof, and a second seat surface on an opposing axial sidethereof.

The catching apparatus may comprise or define a collet sleeve.

The catching apparatus may comprise a tubular portion and a plurality offingers extending longitudinally from the tubular portion. Each fingermay support a respective seat member. A distal end of each finger maysupport a respective seat member. Each finger may be radiallydeformable, for example by longitudinal bending, to permit therespective seat members to be moved radially outwardly and inwardly. Thefingers may be elastically deformable to provide a desired radial bias.

According to a second aspect of the present invention there is provideda method for catching an object, comprising:

arranging a catching apparatus according to any other aspect within apath of travel of an object;

retaining the catching apparatus in a radially extended configuration bya releasable lock arrangement;

releasing the lock arrangement;

configuring the catching apparatus into a catching configuration; and

catching the object.

The method may comprise configuring the catching apparatus into arelease configuration to permit the object to be released.

The method may comprise reconfiguring the catching apparatus to theradially extended configuration after the object has been released.

According to a third aspect of the present invention there is provided amethod for manufacturing a catching apparatus, such as a catchingapparatus according to any other aspect.

The method may comprise deforming the individual collet fingers radiallyoutwardly.

The method may comprise forming the lock arrangement on the catchingapparatus.

The method may comprise forming a lock profile on the catchingapparatus.

According to a fourth aspect of the present invention there is provideda downhole tool comprising a catching apparatus according to any otheraspect.

The downhole tool may comprise a tool housing defining a central boreand including a fluid port. The fluid port may be configured to permitfluid communication between the central bore and a location external tothe housing. The fluid port may extend in any suitable direction. Thefluid port may extend generally perpendicularly relative to the centralbore. In some embodiments the fluid port may extend generally obliquelyrelative to the central bore. The fluid port may extend in varyingdirections, for example portions of the fluid port may extend at leastone of perpendicularly, parallel and obliquely relative to the centralbore.

A valve member, such as a valve sleeve may be mounted within thehousing. The valve member may be moveable, for example axially moveable,from a closed position in which the fluid port is blocked to an openposition in which the fluid port is opened. The fluid port may be openedto provide fluid communication between the central bore of the tool andan external downhole location, such as an annulus, a surroundingformation or the like. The fluid port may be arranged to accommodate oneor both of outflow and inflow.

The downhole tool may comprise a catching apparatus, such as provided inaccordance with any other aspect. The catching apparatus may be mountedwithin the housing, for example on a downhole side of the valve member.

The downhole tool may comprise an indexing mechanism mounted within thehousing. The indexing mechanism may be located on an uphole side of thevalve member. The indexing mechanism may be arranged to be moved axiallyalong the housing towards an actuation site. Upon reaching the actuationsite the indexing mechanism may initiate actuation, for examplemovement, of at least one of the valve member and the catchingapparatus.

The downhole tool may define a downhole fracturing tool.

BRIEF DESCRIPTION OF DRAWINGS

These and other aspects of the present invention will now be described,by way of example only, with reference to the accompanying drawings, inwhich:

FIG. 1 a longitudinal sectional view of a downhole tool which includes acatching apparatus according to an embodiment of the present invention,shown in a radially extended configuration;

FIG. 2 the downhole tool of FIG. 1, reconfigured to a catchingconfiguration prior to receiving an object to be caught;

FIG. 3 the downhole tool of FIGS. 1 and 2 in the catching configuration,after the object has been received;

FIG. 4 the downhole tool of FIGS. 1, 2 and 3, reconfigured to a releaseconfiguration, after the object has been released;

FIG. 5 an enlarged view of a region of the downhole tool shown in FIG.1, showing the catching apparatus.

FIG. 6 an enlarged view of a region of FIG. 5, showing the lockarrangement;

FIG. 7 an enlarged view of a region of the downhole tool shown in FIG.2, showing the catching apparatus.

FIG. 8 an enlarged view of a region of FIG. 7, showing the lockarrangement;

FIG. 9 an enlarged view of a region of the downhole tool shown in FIG.3, showing the catching apparatus.

FIG. 10 an enlarged view of a region of FIG. 9, showing the lockarrangement;

FIG. 11 an enlarged view of a region of the downhole tool shown in FIG.4, showing the catching apparatus.

FIG. 12 an enlarged view of a region of FIG. 11, showing the lockarrangement;

FIG. 13 a longitudinal section view of a collet sleeve of the catchingapparatus;

FIG. 14 a longitudinal section view of an insert sleeve of the catchingapparatus; and

FIG. 15 a longitudinal section view of an annular ring of the catchingapparatus.

DETAILED DESCRIPTION OF DRAWINGS

Referring initially to FIGS. 1 and 5, there is shown a downhole tool,generally identified by reference number 10, according to an embodimentof the present invention. In the illustrated embodiment, the downholetool 10 is for use in treating, for example fracturing, a subterraneanformation 11. The downhole tool 10 comprises a housing 12 which definesa plurality of ports 14 (one port is visible in FIG. 1). A valve sleeve16 is mounted within the housing 12 and is shown in a closed position inFIG. 1, in which the ports 14 are closed and sealed via o-rings 18. Whenin this initial closed position the valve sleeve 16 is pinned to thehousing 12 via a shear pin 19.

A catching apparatus 20, according to an embodiment of the presentinvention, is mounted within the housing 12 on a downhole side of thevalve sleeve 16. The catching apparatus 20 is provided, generally, inthe form of a collet-type sleeve, and comprises a tubular body 22 and aplurality of collet fingers 24 which extend axially from the tubularbody 22. Each finger 24 carries at a distal end thereof a respectiveseat member 26. The catching apparatus 20 defines a longitudinal axis28, which is coincident with the longitudinal axis 29 of the tool 10,and the fingers 24 and seat members 26 are circumferentially distributedaround this axis 28. The fingers 24 are deformable by bending in alongitudinal direction to permit the seat members 26 to be selectivelymoved radially into and out of a central bore or passage 30 defined bythe catching apparatus 20.

In the configuration shown in FIGS. 1 and 5, the seat members 26 arepositioned in a biased radially outward position, received within arecess 32 provided in an insert sleeve 33 disposed within the housing12, and thus removed from the central bore 30. Accordingly, any objectpassing through the tool 10 will not be caught by the catching apparatus20. For example, a passing object may continue past the tool 10 toperform some operation further downhole, for example within a deepertool. In this respect, the catching apparatus 20 may be considered to bepresented in a free configuration in FIGS. 1 and 5.

An activator sleeve 34 is located downhole of the catching apparatus 20,wherein said sleeve 34 defines an activation surface 36 and a stepprofile 38. In the configuration shown in FIG. 1 the activator sleeve 34is secured to the insert sleeve 33 via a number of shear screws 40, andcovers an annular recess 42.

Referring now also to FIG. 6, which shows an enlarged view of a regionof FIG. 5, a lock arrangement 44 is provided for retaining the catchingapparatus 20 is the radially extended free configuration.

In the illustrated embodiment, the lock arrangement 44 comprises a barb46 formed on an external surface 48 of the collet fingers 26 and acorresponding barb 50 formed on an internal surface 52 of a washer ring54 disposed within the housing 12. A corresponding barb 56 is alsoformed on an internal surface 58 of the insert sleeve 33, as will bedescribed further below.

As can be seen, in the configuration shown in FIGS. 1, 5 and 6 the lockarrangement 44 is in a locked condition, in which the barbs 46, 50cooperate to radially restrain movement of the collet fingers 26 and soretain the catching apparatus 20 in the radially extended freeconfiguration.

The washer ring 54 engages a no-go shoulder 60 on the insert sleeve 33and a spring 62 biases at least one, and in the illustrated embodimentboth, of the washer ring 54 and the collet fingers 26 to the engagedposition.

The catching apparatus 20 is configured such that erosion of the seatmembers 26 is minimised when said members 26 are positioned radiallyoutwardly and the apparatus 20 configured in its free configuration, andthe larger surfaces defined by at least one of the barbs may assist inpreventing erosion.

Referring now to FIGS. 2, 7 and 8, the downhole tool 10 is shown in aninitial activated configuration. Specifically, the shear screw 19 hasbeen sheared and the valve sleeve 16 has been axially moved in adownhole direction to open the ports 14 and permit fluid communicationoutwardly from the tool 10. The valve sleeve 16 may be moved by anysuitable actuator, such as via a piston. In some embodiments the valvesleeve may be moved or actuated by an indexing sleeve, such as a colletsleeve disclosed in WO 2011/117601 and/or WO 2011/117602.

During actuation, the valve sleeve 16 acts upon the catching apparatus20, causing this apparatus 20 to also move axially downhole within thehousing 12, moving the barbs 46, 50 out of engagement and driving theseat members 26 out of the recess 32 and onto the activation surface 36of the activator sleeve 34. Relative movement of the catching apparatus20 and activator sleeve 34 is arrested upon engagement of the seatmembers 26 against the step profile 38. Thus, the seat members 26 arepositioned radially inwardly and into the central bore 30 of theapparatus 20. Such a configuration of the apparatus 20 may be considereda catching configuration. That is, any object, such as a ball 64 ofappropriate dimension passing through the tool 10 will engage and seatagainst the seat members 26, thus becoming caught, as shown in FIGS. 3,9 and 10.

In the exemplary embodiment shown in FIGS. 3, 9 and 10, the ball 64 mayfunction to block the tool 10 and establish a flow diversion such thatsubstantially all fluid may be diverted outwardly through the ports 14,for example to fracture a surrounding formation. Further, in someembodiments the ball 64 may have previously operated a system, such asan indexing system, to initially move the valve sleeve 16 and/orcatching apparatus 20.

Referring now also to FIGS. 4, 11 and 12, when the ball 64 is to bereleased the catching apparatus 20 may be reconfigured into a releaseconfiguration. Pressure may be elevated uphole of the ball 64,increasing the force being applied axially on the catching apparatus 20,and also on the activator sleeve 34 via the engagement of the seatmembers 26 with the step profile 38. Upon reaching a predetermined axialforce the shear screws 40 will shear, permitting the catching apparatus20 and activator sleeve 34 to move axially downhole. As such, theannular recess 42 may become uncovered, and upon relief of fluidpressure the spring 62 may move the catching apparatus 20 in an upholedirection (left as shown in the Figures) to permit the seat members 26to become located within the annular recess 42, and allowing the ball 64to be released. By such use, the activator sleeve 34 may function as arelease sleeve.

As shown, the barb 46 engages the barb 56 on the insert sleeve 33, suchthat in the configuration shown in FIGS. 4, 11 and 12 the lockarrangement 44 defines a second locked condition retaining the apparatus20 in a radially extended configuration which permits passage of anobject, such as another ball or a tool, such as a shifting tool, or thelike.

Referring now to FIGS. 13, 14 and 15, there is shown longitudinalsection views, respectively, of the catching apparatus 20 showing thebarb 46, the insert sleeve 33 showing the barb 56 and washer ring 54showing barb 50.

It should be understood that the embodiments described herein are merelyexemplary and that various modifications may be made thereto withoutdeparting from the scope of the present invention.

For example, any suitable lock arrangement may be provided. The lockarrangement may alternatively or additionally comprise a mechanicalretainer, such as a shear pin or the like.

In the exemplary embodiments described the catching apparatus isutilised within a tool which is used for fracturing operations. However,generally, the catching apparatus may be utilised in any situation wherean object must be caught. For example, the catching apparatus mayfunction as an actuator, wherein movement of the apparatus to actuate afurther apparatus or process may be achieved upon or subsequent tocatching an object.

1. A downhole catching apparatus for catching an object, comprising: aplurality of radially moveable seat members arranged circumferentiallyaround a longitudinal axis, wherein the seat members are moveablebetween a radially extended configuration and a radially retractedconfiguration; and a releasable lock arrangement for releasablyretaining the seat members in the radially extended configuration. 2.The downhole catching apparatus according to claim 1, wherein theradially extended configuration permits passage of an object past theseat members, and the radially retracted configuration permits an objectto be caught by the seat members.
 3. The downhole catching apparatusaccording to claim 1, wherein the releasable lock arrangement retainsthe seat members in the radially extended configuration until theoccurrence of an actuation event.
 4. The downhole catching apparatusaccording to claim 1, wherein the lock arrangement defines a lockedcondition and an unlocked condition, and wherein the lock arrangement ismoveable from the locked condition to the unlocked condition to permitmovement of the seat members towards the retracted configuration.
 5. Thedownhole catching apparatus according to claim 4, wherein the lockarrangement is biased towards the locked condition, optionally by abiasing member.
 6. The downhole catching apparatus according to claim 4,wherein the lock arrangement is moveable from the locked condition tothe unlocked condition by axial movement.
 7. The downhole catchingapparatus according to claim 4, wherein the lock arrangement is moveablefrom the unlocked condition to the locked condition to permit the seatmembers to again be retained in the extended configuration.
 8. Thedownhole catching apparatus according to claim 4, wherein the lockarrangement is moveable between the locked condition and the unlockedcondition a plurality of times.
 9. The downhole catching apparatusaccording to claim 1, wherein at least part of the lock arrangement isdefined by a seat member.
 10. The downhole catching apparatus accordingto claim 1, wherein at least pad of the lock arrangement is defined by astructure at least partially surrounding the seat members.
 11. Thedownhole catching apparatus according to claim 10, wherein the structureat least partially surrounding the seat members comprises at least oneof a tool, a housing, an annular member, a sleeve, a ring and a washer.12. The downhole catching apparatus according to claim 1, wherein thelock arrangement comprises a lock profile.
 13. The downhole catchingapparatus according to claim 12, wherein the lock profile comprises anexternal profile formed or otherwise provided on one or more of the seatmembers.
 14. The downhole catching apparatus according to claim 13,wherein the lock profile comprises an internal profile formed orotherwise provided on a structure at least partially surrounding theseat members, wherein the internal and external profiles are configuredto cooperate with each other to selectively provide locking.
 15. Thedownhole catching apparatus according to claim 14, wherein the internaland external profiles are axially moveable relative to each other,wherein in a first relative axial position the internal and externalprofiles are engaged to provide locking, and in a second relative axialposition the internal and external profiles are hot engaged to provideunlocking.
 16. The downhole catching apparatus according to claim 13,wherein the downhole catching apparatus comprises a first internalprofile and a second internal profile, wherein the external profile isconfigured to engage the first internal profile to provide a firstlocked configuration, and to engage the second internal profile toprovide a second locked configuration.
 17. The downhole catchingapparatus according to claim 12, wherein the, or at least one, lockprofile comprises at least one of a hook profile and a barb.
 18. Thedownhole catching apparatus according to claim 12, wherein the, or atleast one, lock profile comprises or defines a geometry with an acuteangle.
 19. The catching apparatus according to claim 1, comprising ahousing, wherein the seat members are located within said housing. 20.The catching apparatus according to claim 19, wherein at least a portionof the locking arrangement is defined by the housing.
 21. The catchingapparatus according to claim 19, wherein at least a portion of thelocking arrangement is provided on a locking structure which is mountedwithin the housing.
 22. The catching apparatus according to claim 21,wherein the locking structure comprises a ring member mounted within thehousing.
 23. The downhole catching apparatus according to claim 1,wherein at least a portion of the lock arrangement is sacrificial toprovide erosion protection.
 24. The downhole catching apparatusaccording to claim 1, comprising an erosion resistant coating.
 25. Thedownhole catching apparatus according to claim 1, for use in catching anobject passing along a flow path within which the catching apparatus islocated.
 26. The downhole catching apparatus according to claim 1,comprising a catching sleeve, wherein the seat members are mounted onsaid catching sleeve.
 27. The downhole catching apparatus according toclaim 1, wherein the catching apparatus is configured to function as atleast one of a flow diverter, a bore plug, a flow restrictor and anactuator when an object is caught.
 28. The downhole catching apparatusaccording to claim 1, for use within a fracturing system or operation.29. The downhole catching apparatus according to claim 1, wherein theseat members are moveable radially inwardly to be retracted into acentral bore of the catching apparatus to define a reduced effectiveinner diameter, and the seat members are moveable radially outwardly tobe radially extended from the central bore to define an increasedeffective inner diameter.
 30. The downhole catching apparatus accordingto claim 29, wherein when the seat members are positioned radiallyinwardly and retracted into the central bore said members are positionedinto the path of an object passing through the catching apparatus, andwhen the seat members are positioned radially outwardly and extendedfrom the central bore said members are outside the path of an objectpassing through the catching apparatus.
 31. The downhole catchingapparatus according to claim 1, wherein the catching apparatus isreconfigured to or in its catching configuration by radially supportingthe seat members in a radially inward position such that outward radialmovement is prevented.
 32. A method for catching an object downhole,comprising: arranging a downhole catching apparatus within a path of anobject travelling downhole, wherein the catching apparatus includes aplurality of seat members which are moveable between a radially extendedconfiguration and a radially retracted configuration; retaining the seatmembers in the radially extended configuration by a releasable lockarrangement; releasing the lock arrangement; causing the seat members tobe radially retracted; and catching the object.
 33. A downhole toolcomprising a catching apparatus, wherein the catching apparatuscomprises: a plurality of radially moveable seat members arrangedcircumferentially around a longitudinal axis, wherein the seat membersare moveable between a radially extended configuration and a radiallyretracted configuration; and a releasable lock arrangement forreleasably retaining the seat members in the radially extendedconfiguration.
 34. The downhole tool according to claim 33, comprising atool housing, wherein the catching apparatus is mounted within the toolhousing.
 35. The downhole tool according to claim 34, wherein the toolhousing defines a central bore and a fluid port, wherein the fluid portis configured to permit fluid communication between the central bore anda location external to the housing.
 36. The downhole tool according toclaim 35, comprising a valve member mounted within the housing, whereinthe valve member is moveable from a closed position in which the fluidport is blocked to an open position in which the fluid port is opened.37. The downhole tool according to claim 34, wherein the catchingapparatus is provided within the housing on one side of the flow portand is arranged to catch an object to permit flow diversion through theflow port.